Investigation of the continuous-wave and pulsed operation of emerging thulium ion-doped laser media around 2000 nm and preparation of ZnS and ZnSe host materials

In recent years, there has been a significant development in thulium ion-doped solid-state gain media capable of generating tunable, coherent laser radiation near 2000 nm. These lasers can operate in continuous-wave (CW), pulsed, and mode-locked modes, and have found applications in various fields such as surgery, spectroscopy, and pumping of mid-infrared optical parametric oscillators. This thesis focuses on successful demonstration of self-Q-switched (SQS) operation of a thulium- doped lutetia (Tm3+:Lu2O3) ceramic laser operating near 2 μm. By optimizing the cavity focusing, SQS operation was achieved at different discrete curved mirror separations without the need of an external modulator. This resulted in the generation of 9.7 μs pulses at the wavelength of 2091 nm and at the repetition rate of 26.7 kHz with 632 mW of pump power at 776 nm. Moreover, a carefully designed resonator was employed to enable low-threshold CW operation with a lasing threshold pump power as low as 33 mW. The CW Tm3+:Lu2O3 ceramic laser exhibited a wide tuning range between 2073 and 2235 nm. This novel achievement paves the way for the development of highly efficient and versatile laser systems in the mid-infrared spectral region. This research also focuses on various synthesis methods for producing thulium ion-doped ZnSe and ZnS solid-state gain media. Currently, single crystal and ceramic laser hosts are manufactured using methods such as the Czochralski process, Floating Zone, and chemical vapor deposition, which are time-consuming, expensive, and involve the use of hazardous chemicals. Alternative methods, including chemical vapor transport (CVT), vertical Bridgman technique for growing single crystals, and spark plasma sintering for producing polycrystalline sampless, have been explored. Herein, ZnSe crystals were successfully obtained from ball-milled powders using the Bridgman technique. The CVT method, by using prereacted powders, resulted in a relatively high optical transmission of up to 40% for a 1.8 mm thick sample. Additionally, we explored the potential of thulium doping through high-energy ball milling as a technique to synthesize gain media for these crystals.